The present invention relates to a manual dispenser of thermoplastic material, particularly depilatory wax. However, such dispenser can also be used for dispensing products having the form of a cream, an ointment, a glue, or a varnish.
In the present specification, thermoplastic materials are intended to encompass all types of materials which assume a solid, semi-solid or pasty physical state at normal room temperature, and are transformed into a liquid or flowable state by application of heat, which then permits, among other things, the material to be spread so as to form a thin layer on a surface. In this dispenser, the material stored in a solid physical state, or form, at normal room temperature can be subjected to a heat flow in order to change into a fluid, and particularly liquid, state in order to be dispensed in the form of a thin layer.
Generally, such a dispenser includes a housing which is constructed to be hand-held, with the interior of the housing being provided with a reservoir containing the thermoplastic material in its solid form. Such solid form can be in the form of granules or a block or bar of, for example, wax. This reservoir can contain means to push the wax toward its outlet, the wax then emerging onto means for distributing a thin layer of molten wax. These distributing means can include an intermediate conduit terminated by an opening from which the layer is deposited directly on a receiving surface, the surface typically being constituted by the skin of a user. Alternatively, the reservoir can have an outlet which opens onto a receiving surface constituted by a transfer surface of an application means, such as a roller for transferring the layer of material onto a surface.
The reservoir, the distribution and/or transfer means and the application means are in thermal communication with heating means to melt the totality or only a proximal portion of the wax in a manner such that, once the wax is in a liquid or flowable state, it flows out of the distributing means in the form of a layer or a band whose thickness depends at least in part on the speed of displacement of the dispenser which moves directly above the application surface, or the peripheral surface speed of the roller. Once the band of wax has been applied to the skin, a band of gauze or of plastic is placed on the wax layer in order to adhere to the wax after the wax has cooled and solidified. When the gauze or plastic band is pulled away from the user's skin, the wax layer is pulled away at the same time, resulting in the removal of hairs which have become imprisoned in the wax layer.
A first type of dispenser permits relatively rapid melting of the extremity of a stick of wax which is pushed through a hot passage whose temperature is controlled and whose outlet opening serves to distribute dots or stripes of wax.
European Patent Document EP-A-0055157 describes such a type of dispenser particularly intended for depilatory removal of hair from the face. In this dispenser, wax in the form of a stick contained in a reservoir is pushed manually into a passage having a first straight part which is surrounded by a heating resistance. Once the wax has been heated to a flowable state, it flows into a second, bent intermediate part of the passage, this second part opening into a dispensing orifice. In order to prevent the melted wax from cooling during its passage through the second part, the passage is made of a material which is a good conductor and accumulator of heat.
In U.S. Pat. No. 1,449,517, a stick of thermoplastic material is pushed manually by means of a toothed wheel into an intermediate heating passage having a conical form with a circumference which decreases toward the outlet. This heating passage is equally composed of a massive metal material and thus requires a long period of time to be heated and has a high degree of thermal inertia.
French Patent Document FR-A-914405 describes an electric dispenser to form wax tablets. In this structure, there is an intermediate dispensing neck downstream of and relatively remote from heating means which are disposed at the outlet of the reservoir containing the stick.
Heating means of dispensers for sticks of wax described above generally have a non-negligible thermal inertia, while the sticks of wax have a relatively low thermal conductivity. The utilization of this type of dispenser is thus tricky since, when the heating means are turned off, passages in contact with the wax do not cool instantaneously, so that the wax continues to melt and flow out of the reservoir for a certain length of time. This additional wax then comes to adhere against the walls of the passage and other adjacent intermediate walls. This causes subsequent restarting of the dispenser to be difficult since it is then necessary to wait not only until the heating passage has returned to its working temperature, but also until all of the wax present in the downstream part of the dispenser has also melted, with the risk that the totality of the stick softens and renders the dispenser unusable as a result of a complete clogging.
Above all, in the dispensers described previously, the wax is heated at its outer surface, i.e. over a surface which is substantially parallel to the axis of displacement of the wax. In addition, it is very difficult to cause the heat to reach the center of the block or stick of wax taking into account the low thermal conductivity of such material. This leads to a local overheating of the wax to accelerate the transfer of heat, thus aggravating the inertia effects of the heating element and creating risks relating to the final application temperature.
German Patent Document DE1 954 812 describes moreover dispensers of mastic which include a main peripheral heating at the level of the outlet of the reservoir opening into a conical intermediate volume which itself terminates at a distribution point. In the embodiment show in FIGS. 4 and 5 of this publication, provision is made for a supplemental heating by means of four electrical resistances arranged in the reservoir outlet in the form of a transverse cross, these being situated upstream of the intermediate conical volume. However, the center of the mastic quadrants thus cut longitudinally in the stick which are still essentially solid when they arrive in the conical intermediate volume where an equalization of the melting is to be effectuated. In addition, when the heating is turned off, the entirety of the surrounding mastic zone is solidified into a single block and it thus takes a long time to soften this material when the heating is restarted despite the arrangement of the heating in the form of a transverse cross.
U.S. Pat. No. 2,272,780 describes a dispenser for meltable colored material used to decorate textiles, this dispenser including heating means constituted by a radiator mounted on electric resistances in the middle of an intermediate chamber situated at the outlet of a reservoir, this chamber opening onto a distributing ball valve. As shown in the drawings of this patent document, the radiator is present in the form of a transversal disk surmounted in the downstream direction by four blades arranged in the form of a cross, the molten material having to flow around the disk in order to reach the valve. This radiator is relatively massive and, when the heating means are shut off, the material solidifies in all of the chamber, which retards subsequent restarting of the dispenser.
A second type of dispenser, called a "roller dispenser", permits spreading of a layer of wax in the form of a band on an application surface and is described in the patent documents FR-A-2520601, FR 2 706 261, EP 499 317 and U.S. Pat. Nos. 3,103,689 and 5,556,468. These dispensers comprise a transfer and application roller disposed across the outlet of an intermediate zone situated in an extension of a reservoir outlet, the space between this intermediate zone and the roller constituting the surface for distributing the wax as a sheet on the periphery of the transfer roller.
In the embodiment according to the document FR-A-2520601, the dispenser is preliminarily installed in a heating sleeve within a support housing for the time necessary for the entirety of the wax contained in the reservoir to melt. Therefore, the time that one must wait until the dispenser is ready for use is particularly long.
In the embodiment described in FR 2 706 261, and U.S. Pat. No. 5,556,468 a reservoir made of aluminum includes a central diffusion blade and is heated by an electric resistance placed against one of its longitudinal walls. It is equally necessary, in this case, to wait until all of the wax in the reservoir is melted before being able to use the dispenser.
In the embodiments disclosed in the documents EP 499 315 and U.S. Pat. No. 3,103,689 a single electrical resistance is arranged in the intermediate zone slightly above and parallel to the roller. If desired, the resistance is completed by a fin which is oriented toward the roller in order to also heat it. Starting of the dispenser can only commence after all of the wax present in the intermediate zone has melted.
In summary, depilatory hair removal can generally begin in these configurations only when the totality of the wax present in the reservoir and/or in the intermediate zone at the outlet of which the roller is located has melted and comes in contact with the transfer surface of the applicator roller, which requires the user to wait for a non-negligible time after having turned the dispenser on. This waiting time is undesirable because it prevents a rapid hair removal operation when the user is in a hurry.
Conversely, when the hair removal operation has ended and the user turns off the heating means, the remainder of the molten wax continues to move forward during a certain time period and accumulates between the heating means and the roller, where that wax solidifies. This phenomenon of blocking the space between the outlet and the distribution element then results in possible complete blockage of the applicator roller against rotation. When the dispenser is again placed in operation, this portion of the wax will require even more time to melt since it is not in direct contact with the heating means.
Moreover, the thickness of the band of wax is hard to control by the user because it is linked to the geometry and the composition of the wax.